The present invention is generally related to computed tomography (CT) and electron beam tomography (EBT) scanning devices and methods. More specifically, the present invention is related to improving a time resolution of a CT and EBT scanning device.
In an x-ray CT scanner, an x-ray tube is rotated around the body and transmits x-rays through the patient to a rotating detector array or fixed detector array. In this way multiple absorption rays of the patient are obtained. Many algorithms exist today to reconstruct the absorption values as an image that represents the local attenuation of x-rays of the body tissues of the patient that are imaged.
In a conventional mechanical CT scanner, the x ray tube output is generally fan-shaped, with a fan angle of approximately sixty degrees. Typically, the x-ray tube moves through a complete 360 degree rotation to obtain a full data set for a single tomograph. Reconstruction of the tomograph, however, can be reconstructed from a less than full attenuation data set (e.g., less than 360 degrees of rotation, e.g., 180 degrees plus the fan beam arc). Thus, if the tube gantry rotation time is 500 msec, the data needed to acquire an image will require over 333 msec of acquisition time. Unfortunately, an organ such as the heart, will typically have undergone half of its cyclical motion in that time, and the image will exhibit blur and motion artifacts.
In an EBT scanner, rather than a moving x-ray tube, the detectors are fixed and an x-ray beam is scanned or directed across a target tissue from different points of a tungsten target arc that is impinged upon by a steered beam of electrons. Mathematically, the reconstruction process is the generally the same for an EBT scanner as for a mechanical CT scanner, except that the electron beam can be scanned faster than an x-ray tube can be moved. Consequently, the imaging time of a patient is faster and is typically between approximately 50 msec to approximately 100 msec for each slice.
While EBT scanners are faster than mechanical CT scanners, EBT scanners still may not meet the requirements of processes that require better time resolution than can be provided by the conventional CT scanners and EBT scanners.
For the above reasons, what are needed are methods and devices that improve the time resolution of mechanical and electron beam CT scanners.